If the /etc/exports file exports a directory to an IP address, and a PTR
record exists for that IP in DNS, mounting that export from the specified
machine fails.
Changing the IP address to the DNS name in the exports file and restarting
the NFS server causes the mount to succeed.

Get serious! I reported this bug three years ago, as a good faith gesture. I
don't use RH7.0 anymore -- I don't even use NFS anymore.
Either the bug's been fixed, or it is still there. If you're conscientious,
you'll check - which means finding out why it failed in the first place, and
when/how it got fixed. Putting the onus on me, after three years, to do your QA
for you -- "ooh, I need more information from the customer, or I'm helpless" --
is a bit much. Assuming that everything's OK just because you can't reproduce on
the current release is sloppy.
While I recognize that the person now asking for more info probably isn't the
one who has ignored the bug report these long years, I also recognize a cop-out
when I see one. 'Scuse the flame, but thinking about the 'net three years ago
made me nostalgic.